I've no doubt Sorceress wins in 100% run. For normal mode run, the problem is hitting L18 in time to use Teleport - and that's the big issue. For the Assassin, hitting L6 is very quickly done in comparison to the length of a run, for Burst of Speed. This will come as a consequence of running through the areas Blood Moor, Cold Plains, Stony Field, Underground Passage, Dark Woods, Tamoe Highlands, Outer Cloister, Barracks, Jail, Inner Cloister, Catacombs, in order, picking off whatever uniques and superuniques happen to be in the way of all that. It may also be worth visiting Tristram for a nice experience boost there - it can be very often populated with more than half a dozen combined champion and boss packs.
Even with all this considered, it still takes a good 20-25 minutes to run through, while levelling to hit L12 - which both Assassin and Sorceress need for their best killing skills in a Normal playthrough. Sorc should be pumping Fire Bolt for Fire Ball synergy, and Assassin Fire Blast for Wake of Fire. Fire spells are an obvious choice, since Andariel has a nice weakness to Fire, as well as the possibility of using Leaf runeword staff for a great boost there.
Hitting L6 can be done very quickly for an Assassin, and she'll have the benefit of that skill for the entire run. For a sorceress, hitting L18 will come quite late - maybe in Act 3 if no time is spent dedicating time to levelling her. For a TAS, remember, there will be no save-loading to take advantage of, so superuniques can't be killed multiple times and manipulating lots of experience shrines will be a difficult challenge, if the game allows for it at all.
Another thing to consider is that, without a nice amount of +skills gear, Teleport at L1 is very expensive to cast, and it will burn through her mana like nothing. Assassin is obviously less potion-intensive in this respect, should need to spend very little time shopping for potions can keep herself going by collecting what gets dropped along the way.
